This invention relates to a fuse used for protecting an automotive electric circuit or the like, and more particularly to an improved fuse in which a fuse body is housed and held in a housing provided with a cover.
FIGS. 6 and 7 show a related-art fuse used for protecting an electric circuit in an automobile or the like.
A fusible link 1 is a so-called plug-in type fuse, and comprises a fuse body 2 made of a metal sheet, a housing 3 which is made of an insulative resin, and has the fuse body 2 housed and held therein (the fuse body 2 is inserted into the housing 3 through a rectangular upper opening), and a cover 4 which is made of an insulative resin, and covers the upper opening in the housing 3.
As shown in FIG. 7, the fuse body 2 includes a strip-like fusible conductor 10 having a melting portion 10a, and a pair of female terminals 11 and 11 which are formed respectively at both ends of the fusible conductor 10, and can be fittingly connected respectively to mating tab terminals 15 formed on a circuit provided at a fuse receiving portion 13. This fuse body 2 is formed into an integral construction, using a metal sheet.
The cover 4 includes a lid 5 in the form of a generally rectangular plate, and a pair of locking pieces 6 extending downwardly respectively from opposite end edges of the lid 5, and this cover 4 is molded into an integral construction, using a transparent plastic material. Retaining projections 7 are formed on and project respectively from those side walls (peripheral wall) of the housing 3 corresponding respectively to the locking pieces 6. When the pair of elastic locking pieces 6 are retainingly engaged with the retaining projections 7, respectively, the cover 4 is locked to the housing 3 in such a manner that this cover 4 covers the upper opening in the housing 3.
As shown in FIG. 7, the fusible link 1 is mounted in the fuse receiving portion 13 formed at an electric connection box such as a relay box, and the fuse body 2 is electrically connected to the mating tab terminals 15. A fuse guide wall 14 for supporting the housing 3 is formed at the fuse receiving portion 13, and this fuse guide wall 14 serves to guide the mounting insertion of the fusible link 1, and also serves to prevent the fusible link 1 from being displaced out of position after the fusible link 1 is mounted.
In recent years, electric connection boxes have increasingly been required to have a compact and lightweight design and a reduced cost, and in this connection fuses also have been required to have a compact and lightweight design.
Therefore, for example, when a fuse body 22 as well as a housing 23 has a compact design (a reduced height) as in a fusible link 21 shown in FIG. 8, this fusible link 21 can be much more reduced in size and weight as compared with the fusible link 1 shown in FIG. 7.
And besides, since the fusible link 21 has the compact design and the reduced height, a cover of an electric connection box can be reduced in height, so that the compact and lightweight design of the electric connection box is also achieved.
In the fuse body 22, secondary (subsequent) short-circuit or the like must be prevented when a fusible conductor 28 melts, and therefore it is difficult to further reduce the distance between a pair of female terminals 29.
Therefore, horizontal dimensions and shapes of the fuse body 22 and housing 23 are substantially the same as those of the fuse body 2 and housing 3 of the fusible link 1, and a cover 24 has the same shape as that of the cover 4, and the cover 24 is locked to the housing 23 by locking pieces 26 retainingly engaged respectively with retaining projections 27 formed on and projecting from a peripheral wall of the housing 23.
However, when the fusible link 21 is to be mounted in the fuse receiving portion 13 formed at the electric connection box such as a relay box, as shown in FIG. 8, the locking pieces 26 interfere with an upper edge of the fuse guide wall 14, so that this fusible link 21 can not be mounted in the proper position in the fuse receiving portion 13.
Therefore, it is necessary to take countermeasures such as the reduction of the height of the fuse guide wall 14 and the formation of notches for preventing the interference. However, such countermeasures for the fuse guide wall 14 will incur a change of a mold for molding an electric connection box body and a complicated construction of the mold, so that the cost greatly increases.
When the locking pieces 26 of the cover 24 are shortened so as to prevent the interference thereof with the upper edge of the fuse guide wall 14, each locking piece 26 is less elastically deformed when it slides over the retaining projection 27. Incidentally, when each retaining projection 27 is reduced in height so that the locking piece 26 can easily slide over the retaining projection 27, a sufficient retaining force can not be obtained, and the cover 24 can be easily disengaged from the housing.
When the locking pieces 26 are shortened, and therefore are less elastically deformed, there are anxieties that the cover 24 can not be easily fitted on the housing, and that each locking piece 26 is damaged at its proximal end portion on which an excessive force acts.
It is therefore an object of this invention to provide a fuse having a compact and lightweight design while being provided with a cover having locking pieces which are prevented from damage.
In order to achieve the above object, according to the invention, there is provided a fuse, comprising:
a fuse body, provided with a fusible element;
a housing body, containing the fuse body therein, and formed with an opening and a retaining projection arranged in the vicinity of the opening; and
a cover body, formed with a locking piece adapted to engage with the retaining projection so that the cover body closes the opening,
wherein a rigidity-reduced portion is formed in the cover body, so that the cover body can be flexed substantially without flexing the locking piece, at least when the locking piece engages with the retaining projection.
In such a configuration, even when the locking piece is short, the cover body itself is elastically deformed at the rigidity-reduced portion so that the locking piece can be displaced in the disengaging directions respectively relative to the retaining projection.
Since an excessive force will not act on the locking piece which is displaced so as to slide over the corresponding retaining projection, damage to the locking pieces is prevented.
Therefore, there can be obtained the compact and light-weight fuse provided with the cover body having the relatively short locking piece.
Preferably, the rigidity-reduced portion is a recessed portion formed in a face of the cover body to be opposed to the opening.
In such a configuration, merely by forming the recessed portion in the cover body, the rigidity-reduced portion which enables the elastic deformation of the cover body can be easily formed. Further, by suitably determining the width and depth of the recessed portion, the retaining force of the locking piece can be arbitrarily adjusted.
Preferably, the locking piece includes a pair of locking pieces, which are arranged symmetrically with respect to the rigidity-reduced portion.
Preferably, the fusible element is exposed through the opening, in a case where the cover body does not close the opening.